: The long-term objective of this proposal is to develop a genomic and proteomic 'fingerprint' of heroin self-administration. This will be accomplished by comparing changes in mRNA and protein levels from medium spiny neurons of the nucleus accumbens (NAc) between heroin self-administering mice and yoked-heroin and saline controls. It is hypothesized that heroin administration will induce changes in mRNA and protein levels in the NAcc neurons that are specific to the means of administration, i.e. self-administration vs. yoked-controls. This hypothesis will be tested using a variety of techniques. Single cell mRNA amplification will be used to produce probes for screening Incyte cDNA GEM arrays as well as custom made 'neuroarrays'. Differential changes in mRNA seen using the arrays will be confirmed using in situ hybridization and real-time PCR. The results of these mRNA experiments will be used to identify target proteins, which will be examined using immuno-histochemistry as well as a newly developed proteomic technique, IDAT, which allows for the examination of 100s of proteins at a time. The establishment of a genomic and proteoinic fingerprint will lead to a better understanding of heroin abuse and could eventually lead to more effective treatments as well as identification of molecular risk factors associated with substance abuse.